Friction welding

Description

[0001] The present invention relates to friction welding and in particular to the use of a shielding gas in the friction welding process.

[0002] Friction welding is used in the manufacture or repair of components such as integrally bladed rotor assemblies. Separately made blades are attached to the periphery of a disc or drum by their roots. The disc or drum is held stationary whilst the blades are reciprocated under pressure to develop the necessary weld temperature.

[0003] Friction welding is generally less susceptible to oxidation defects than conventional welding processes. The relative movement between the components prevents the ingress of ambient air into the weld and any oxides are transported away by the extruded material. Nevertheless defects have been discovered in the edge and corner regions of the weld, which could affect the integrity of the weld.

[0004] To prevent the formation of defects in the edge and corner regions of the weld it is known to use a shielding gas. French patent number 2 760 985 B1 discloses flowing a shielding gas through orifices in a nozzle to drive away oxygen. The nozzle is shaped to envelop the blade being welded onto a disc. A problem with this arrangement is that the nozzle extends into the weld area where space is restricted.

[0005] A method according to the preamble of claim 1 is disclosed in US-A-6 160 237.

[0006] The present invention seeks to provide an improved method of friction welding in which a shielding gas envelops the weld area without the need for a shaped nozzle that extends into the weld area.

[0007] According to the present invention a method of friction welding according to claim 1 is provided

[0008] Preferably the opposing flows of shielding gas are introduced at an angle to the interface. The primary nozzles may be conical to diffuse the shielding gas and prevent turbulence. The primary nozzles introduce the shielding gas at a flow rate of the order of 40-150 litres/minute.

[0009] In a further embodiment of the present invention secondary nozzles are provided to direct a further flow of shielding gas towards the primary nozzles. The secondary nozzles introduce the shielding gas at a flow rate of the order of 25 litres/minute.

[0010] Preferably the shielding gas is an inert gas such as argon.

[0011] In the preferred embodiment of the present invention the first and second workpieces are preferably a disc and a blade of a rotor assembly.

[0012] A gas chamber may be created around the weld interface, which is partially sealed. In the preferred embodiment of the present invention the blades adjacent the weld interface define the partially sealed chamber.

[0013] The present invention will now be described with reference to the accompanying figures in which;

[0014] Figure 1 shows apparatus suitable for friction welding blades onto a rotor disc.

[0015] Figure 2 is a pictorial view of part of a rotor disc showing the flow of a shielding gas introduced in accordance with one embodiment of the present invention.

[0016] Figure 3 is a pictorial view of part of a rotor disc showing the flow of shielding gas introduced at an angle in accordance with a second embodiment of the present invention.

[0017] Figure 4 is a pictorial view of part of a rotor disc showing the flow of shielding gas through a plurality of nozzles in accordance with a further embodiment of the present invention.

[0018] Referring to figure 1 a disc 10 is held between an upper clamp member 12 and a lower clamp member 14. An axial compression force is applied between the clamp members 12 and 14 to hold the disc 10 in a fixed relationship during friction welding.

[0019] In the arrangement shown in figure 1 an elongate rigid member, in the form of a pull rod 13, extends axially and provides the axial compression force between the clamp members 12 and 14. A mechanism 16 generates the clamp force on the pull rod 13. The pull rod 13 has a head 15 adapted to urge the upper clamp member 12 downwards towards the lower clamp member 14 to grip the disc 10.

[0020] A pin 17 is used to key the lower clamp member 14. The lower clamp member 14 can then be indexed between allowable orientations relative to the welding station 18.

[0021] The upper and lower clamp members 12 and 14 carry the disc 10 and can be indexed around so that further workpieces, such as blades 20, can be attached at different positions on the periphery of the disc 10 by the welding station 18.

[0022] A blade 20 is mounted in a component holder on the welding station 18. The blade 20 is oscillated with respect to the disc 10 whilst a weld generating force is applied in a generally radial direction as indicated by arrow A. Temperatures are generated at the interface between the disc 10 and the blade 20, which are sufficient to weld them together. A number of blades 20 are friction welded to the periphery of the disc 10 to form an integral structure called a blisk. It is envisaged that component discs 10 could be welded together to form a drum to which the blades 20 could be subsequently attached. Thus the arrangement described may be used to clamp either a single disc 10 or a drum assembly (not shown).

[0023] To minimise defects due to oxidation a shielding gas is introduced at the weld interface. The shielding gas is an inert gas, such as argon.

[0024] In the embodiments shown in figures 2 and 3, opposing flows of argon are introduced through two primary nozzles 22 and 24. The primary nozzles 22 and 24 are circumferentially spaced apart and are located on opposite sides of the weld interface. The two opposing gas flows create a gas curtain, shown by the arrows in figure 2 and 3, which flows around the weld interface. The gas curtain shields the weld interface from air and so reduces the formation of defects due to oxidation.

[0025] The primary nozzles 22 and 24 may introduce the gas flow in a generally axial direction as shown in figure 2 or at an angle as shown in figure 3.

[0026] To maintain the effectiveness of the shielding gas curtain the flow must be laminar. The opposing shielding gas flows are therefore introduced at a low velocity and a high flow rate to reduce turbulence. In embodiments of the present invention shown in figure 2 and 3 the primary nozzles 22 and 24 are conical and filled with wire wool. The conical nozzles 22 and 24 act as diffusers to reduce the velocity of the shielding gas and prevent turbulence. The gas flow rate, from each of the primary nozzles 22, 24, is of the order of 40 litres/minute.

[0027] As the shielding gas exits from the primary nozzles 22 and 24 oxygen could be drawn into it from the surrounding ambient air. This is prevented by shielding the primary nozzles 22 and 24 with part of the gas curtain. The part of the gas curtain indicated by the arrows B flows over the primary nozzles 22 and 24 prevents the ingress of oxygen from the ambient air.

[0028] Figure 4 shows a further embodiment of the present invention in which the shielding gas is introduced through primary nozzles 26-36 and secondary nozzles 38,40.

[0029] Three primary nozzles 26,28,30 are located on one side of the weld interface and three further primary nozzles 32,34,36 are located on the opposite side of the weld interface. It will however be appreciated by one skilled in the art that any number of primary nozzles could be used depending upon the particular welding application.

[0030] The secondary nozzles 38,40 introduce a backing flow of shielding gas in the direction of arrows C. The backing flow is directed towards the primary nozzles 26-36. The secondary nozzles 38,40 are located adjacent the extremities of the weld interface and encourage the shielding gas from the primary nozzles 26-36 to flow around the extremities of the weld interface. The backing flow from the secondary nozzles 38,40 thus ensures adequate shielding at the weld extremities. The backing flow from the secondary nozzles 38,40 also further shields the primary nozzles 26-36 from the ingress of ambient air.

[0031] In the preferred embodiment of the present invention the secondary nozzles 38,40 introduce the backing flow at a flow rate of the order of 25 litres/minute.

[0032] In the embodiments shown, blades 20 are fastened either side of the blade to be friction welded. The adjacent blades define a partially sealed gas chamber around the weld interface. The gas chamber defined by the adjacent blades helps to maintain the gas-shielding curtain around the weld interface.

[0033] It will however be appreciated by one skilled in the art that other means may be used to define an appropriate gas chamber and that the gas chamber may be fully or partially sealed.

Claims

1. A method of friction welding workpieces together at an interface having two opposite sides and extremities at either end thereof comprising the steps of holding a first workpiece (10) in a fixed relationship to a second workpiece (20), oscillating the second workpiece (20) with respect to the first workpiece (10), applying a load between the first and second workpieces (10,20) so as to generate a temperature at the interface between the workpieces (10,20) which is sufficient to weld the workpieces (10,20) together, introducing opposing flows of a shielding gas through primary nozzles (22,24) located at the extremities of the interface, at least one primary nozzle (22 or 24) being provided at each extremity of the interface and spaced apart characterised in that the primary nozzles (22,24) at either extremities of the interface are located on opposite sides of the interface to provide opposing flows on the opposite sides of the interface, a part of each of the opposing flows passing around the extremities of the interface, whereby a continuous laminar flow of shielding gas around the interface is produced.

2. A method of friction welding as claimed in claim 1
characterised in that the opposing flows of the shielding gas are introduced at an angle to the extremities of the weld interface.

3. A method of friction welding as claimed in claim 1 or claim 2 characterised in that the primary nozzles (22,24) are conical.

4. A method of friction welding as claimed in any preceding claim characterised in that secondary nozzles (38,40) are provided to direct a further flow of shielding gas towards the primary nozzles (22,24).

5. A method of friction welding as claimed in claim 4,
characterised in that the secondary nozzles (38,40) introduce a flow of shielding gas at a rate of the order of 25 litres/minute.

6. A method of friction welding as claimed in any of claims 1-5, characterised in that the first and second workpieces (10,20) are a disc and a blade of a rotor assembly.

7. A method of friction welding as claimed in any preceding claim characterised in that a gas chamber is created around the weld interface.

8. A method of friction welding as claimed in claim 7,
characterised in that the gas chamber is partially sealed.

9. A method of friction welding as claimed in claim 7, or claim 8 characterised in that the gas chamber is defined by the blades (20) adjacent the weld interface.

10. A method of friction welding as claimed in any preceding claim characterised in that the shielding gas is inert.

11. A method of friction welding as claimed claim 10,
characterised in that the shielding gas is argon.

12. A method of friction welding as claimed in any of the preceding claims characterised in that the opposing flows of shielding gas are introduced at a rate of 40-150 litres/minute.

Ansprüche

1. Verfahren zum gegenseitigen Verbinden von Werkstücken durch Reibschweißen an ihrer Berührungsfläche, die gegenüberliegende Seitenkanten und gegenüberliegende, im Abstand zueinander angeordnete Stirnkanten an beiden Enden aufweist, mit den folgenden Schritten:

es wird ein erstes Werkstück (10) fest gegenüber einem zweiten Werkstück (20) angeordnet;

es wird das zweite Werkstück (20) gegenüber dem ersten Werkstück (10) in Schwingungen versetzt;

es wird eine Belastung zwischen dem ersten und zweiten Werkstück (10, 20) derart ausgeübt, dass eine Temperaturerhöhung an der Berührungsfläche zwischen den Werkstücken (10, 20) auftritt, die ausreicht, um die Werkstücke (10, 20) miteinander zu verschweißen;

es werden gegenüberliegend Strömungen eines Abschirmgases durch Primärdüsen (22, 24) eingeführt, die an den Stirnkanten der Berührungsflächen angeordnet sind;

es wird wenigstens eine Primärdüse (22) oder (24) an der Stirnkante der Berührungsfläche im Abstand dazu angeordnet, dadurch gekennzeichnet, dass die Primärdüsen (22, 24) an beiden Stirnkanten der Berührungsfläche an gegenüberliegenden Seitenrändern der Berührungsfläche angeordnet sind, um entgegengesetzt gerichtete Strömungen auf die gegenüberliegenden Seitenkanten der Berührungsfläche zu richten, wobei ein Teil jeder entgegengesetzten Strömung dann über die Stirnkanten der Berührungsfläche strömt, wodurch eine kontinuierliche laminare Strömung des Abschirmgases um die Berührungsfläche herum erzeugt wird.

2. Verfahren zum Reibschweißen nach Anspruch 1, dadurch gekennzeichnet, dass die entgegengesetzt gerichteten Strömungen des Abschirmgases unter einem Winkel den Stirnkanten der Schweißberührungsfläche zugeführt werden.

3. Verfahren zum Reibschweißen nach Anspruch 1 oder Anspruch 2, dadurch gekennzeichnet, dass die Primärdüsen (22, 24) konisch ausgebildet sind.

4. Verfahren zum Reibschweißen nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass Sekundärdüsen (38, 40) vorgesehen sind, um eine weitere Strömung von Abschirmgas auf die Primärdüsen (22, 24) zu richten.

5. Verfahren zum Reibschweißen nach Anspruch 4, dadurch gekennzeichnet, dass die Sekundärdüsen (38, 40) eine Strömung von Abschirmgas mit einer Menge in der Größenordnung von 25 Litern pro Minute einführen.

6. Verfahren zum Reibschweißen nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, dass das erste und das zweite Werkstück (10, 20) die Rotorscheibe und eine Laufschaufel eines Rotoraufbaus sind.

7. Verfahren zum Reibschweißen nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass eine Gaskammer rund um die Schweißberührungsfläche erzeugt wird.

8. Verfahren zum Reibschweißen nach Anspruch 7, dadurch gekennzeichnet, dass die Gaskammer teilweise abgedichtet ist.

9. Verfahren zum Reibschweißen nach Anspruch 7 oder Anspruch 8, dadurch gekennzeichnet, dass die Gaskammer durch die Laufschaufeln (20) benachbart zur Schweißberührungsfläche definiert wird.

10. Verfahren zum Reibschweißen nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass das Abschirmgas inert ist.

11. Verfahren zum Reibschweißen nach Anspruch 10, dadurch gekennzeichnet, dass das Abschirmgas Argon ist.

12. Verfahren zum Reibschweißen nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass die entgegengesetzten Strömungen des Abschirmgases mit einer Menge von 40 bis 150 Litern pro Minute zugeführt werden.

Revendications

1. Procédé pour souder ensemble par friction des pièces au niveau d'une interface ayant deux côtés opposés et des extrémités au niveau de chacune de ses extrémités, comprenant les étapes consistant à maintenir une première pièce (10) selon une relation fixe par rapport à une seconde pièce (20), faire osciller la seconde pièce (20) par rapport à la première pièce (10), appliquer une charge entre les première et seconde pièces (10, 20) afin de générer une température au niveau de l'interface entre les pièces (10, 20) qui est suffisante pour souder les pièces (10, 20) ensemble, introduire des écoulements opposés d'un gaz protecteur par les buses principales (22, 24) situées aux extrémités de l'interface, au moins une buse principale (22 ou 24) étant prévue à chaque extrémité de l'interface et espacée, caractérisé en ce que les buses principales (22, 24) à chaque extrémité de l'interface sont situées sur les côtés opposés de l'interface pour fournir des écoulements opposés sur les côtés opposés de l'interface, une partie de chacun des écoulements opposés passant ensuite autour des extrémités de l'interface, moyennant quoi, un écoulement laminaire continu de gaz protecteur autour de l'interface est produit.

2. Procédé pour souder par friction selon la revendication 1, caractérisé en ce que les écoulements opposés de gaz protecteur sont introduits selon un angle par rapport aux extrémités de l'interface de soudure.

3. Procédé pour souder par friction selon la revendication 1 ou la revendication 2, caractérisé en ce que les buses principales (22, 24) sont coniques.

4. Procédé pour souder par friction selon l'une quelconque des revendications précédentes, caractérisé en ce que des buses secondaires (38, 40) sont prévues pour diriger un écoulement supplémentaire de gaz protecteur vers les buses principales (22, 24).

5. Procédé pour souder par friction selon la revendication 4, caractérisé en ce que les buses secondaires (38, 40) introduisent un écoulement de gaz protecteur à une vitesse de l'ordre de 25 litres / minute.

6. Procédé pour souder par friction selon l'une quelconque des revendications 1 à 5, caractérisé en ce que les première et seconde pièces (10, 20) sont un disque et une pale d'un ensemble de rotor.

7. Procédé pour souder par friction selon l'une quelconque des revendications précédentes, caractérisé en ce qu'une chambre de gaz est créée autour de l'interface de soudure.

8. Procédé pour souder par friction selon la revendication 7, caractérisé en ce que la chambre de gaz est partiellement hermétiquement fermée.

9. Procédé pour souder par friction selon la revendication 7 ou la revendication 8, caractérisé en ce que la chambre de gaz est définie par les pales (20) adjacentes à l'interface de soudure.

10. Procédé pour souder par friction selon l'une quelconque des revendications précédentes, caractérisé en ce que le gaz protecteur est inerte.

11. Procédé pour souder par friction selon la revendication 10, caractérisé en ce que le gaz protecteur est de l'argon.

12. Procédé pour souder par friction selon l'une quelconque des revendications précédentes, caractérisé en ce que les écoulements opposés de gaz protecteur sont introduits à une vitesse de 40 - 150 litres / minute.

Drawing